Hitherto, in a power generation plant which uses a steam turbine, a gas turbine, or a combined cycle including the steam turbine and the gas turbine, it is known that when a rotor (rotary shaft) is left while not being rotated at a high temperature during a period of time when operation is stopped, the following phenomenon occurs. That is, as the temperature of steam or gas decreases, a temperature gradient occurs in a turbine casing in a vertical direction, and thus bending occurs in the rotor due to thermal expansion, or a small degree of bending occurs during a period of time when the turbine is stopped due to the rotor's own weight.
Therefore, during a period of time when the operation of the turbine is stopped or before starting-up, so-called turning, in which the rotor is rotated at a low speed for a predetermined time is performed to prevent the occurrence of bending in the rotor.
For example, a turning device described in PTL 1 includes a driving motor. The shaft of the driving motor is connected to a deceleration mechanism which decelerates the rotation of the shaft. The deceleration mechanism is provided with a driving pulley (driving wheel) and is configured to transmit the rotation of the decelerated driving motor to the driving pulley.
On the lower side of the deceleration mechanism, a driven pulley (driven wheel) having the same axial direction as that of the driving pulley is disposed. A V-belt (annular member) is looped over the driving pulley and the driven pulley.
A first spur gear which rotates coaxially with the driving pulley is integrally attached to the driving pulley. On the lower side of the first spur gear, a second spur gear having the same axial direction as that of the first spur gear is disposed. The first spur gear and the second spur gear always engage with each other.
A pair of arm members are supported by the rotary shaft of the second spur gear so as to be inclined while interposing the second spur gear therebetween in the axial direction thereof. A pinion gear (second toothed wheel) having the same axial direction as those of the second spur gear and a wheel gear is rotatably pivoted by one end portion of the arm member. The pinion gear is displaceable by the inclination of the arm member between an engagement position where the pinion gear approaches and engages with the wheel gear and a retreat position where the pinion gear is separated from the wheel gear toward a radially outer side. The wheel gear is coaxially fixed to a rotor.
As described above, in the turning device described in PTL 1, gears which transmit the driving force to the wheel gear on the downstream side from the driven pulley have a three-stage configuration including the first spur gear, the second spur gear, and the pinion gear.
In general, one end portion of the rotor is connected to a compressor, and the other end portion of the rotor is connected to a turbine. The connection portion of the rotor and the compressor is covered with a coupling guard for avoiding oil or the like.
The driving pulley and the driven pulley are covered with a chain cover (cover), and the chain cover is detachably attached to the compressor side of the turning device.
In the turning device configured as described above, the position of the pinion gear is the retreat position during an operation of a steam turbine.
When the operation of the steam turbine is stopped, the arm member is inclined by a control unit of the turning device such that the pinion gear is displaced from the retreat position toward the wheel gear to the engagement position. When the driving motor is driven, the rotation power of the driving motor is transmitted to the wheel gear via the deceleration mechanism, the driving and driven pulleys, the V-belt, the first spur gear, the second spur gear, and the pinion gear. In addition, the rotor is rotated along with the wheel gear. At this time, the rotor is rotated at a lower speed than when the steam turbine is operated.